Preheat the oven to 375 degrees F. Spray a 7x11 baking dish with nonstick baking spray.
Add the flour, oats, both sugars, and cinnamon to a medium bowl. Stir to combine.
Add the butter to the dry ingredients. Using a spatula, fork, or your hands, work the butter into the dry ingredients until the butter has coated all of the dry ingredients and clumps together.
Break apart the big clumps, cover, and place in the freezer to firm up. Begin working on the pumpkin filling.
Pumpkin Filling
In a large bowl, add in the pumpkin puree, both sugars, and pumpkin pie spice. Stir to combine.
Add in the vanilla extract and eggs. Stir with a spatula or whisk until the eggs are worked into the filling.
Add in the evaporated milk and stir until there are no more white milk streaks in the filling.
Pour the pumpkin filling into the prepared baking dish.
Place in the oven and bake for 20 minutes until it has thickened up some in the center.
Pull the baking dish out of the oven and sprinkle the crisp topping all over the top.
Place back in the oven and bake for an additional 25 minutes until the center of the crisp is set up and the crisp topping is golden brown.
Let cool completely and serve. Top with whipped cream.